Conventional electrical power outlets or outlet strips have fixed plug holes that are generally left open. If water leaks into those open plug holes, it will cause electrical accident that may lead to property damage or even bodily harm to humans. The limited number of plug holes on a conventional electrical outlet or outlet strip limits the plug-in locations, which further limits the locations and positioning of household appliances. For example, if a household appliance is located relatively far away from the plug holes, it may not be directly plugged into the outlet or outlet strip with its own power cord. In this situation, an extra power cord or outlet strip is needed.